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From: N1BUG <paul@n1bug.com>
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Message-ID: <0e1a6a86-5665-9e79-4a59-a51d3850c8f4@n1bug.com>
Date: Tue, 10 Apr 2018 20:41:20 -0400
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Subject: Re: LF: W1VD amp help - IR2110 and timing
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Reply-To: rsgb_lf_group@blacksheep.org

Andy, Jay, all

The next thing you're probably going to tell me is to remember the
flux density equation when designing such a thing. :-) I have yet to
grasp how to work with that. To me it's a vicious killer out to eat
me alive!

I apologize if I am irritating people over-posting with this. As for
clutching at straws, I am desperately doing just that. In 37 years
licensed I have never been so excited about or consumed by a passion
for radio as I am about LF. I desperately want to reach full legal
EIRP but as you've no doubt noted in recent months my quest is not
going well when it comes to amplifiers.

I chose this particular design, despite not liking the 2Fo drive
requirement, precisely because so many have been built and worked
and because it's relatively affordable. I *thought* I could
successfully duplicate the work of so many others but it seems
perhaps not!

I don't come here blindly begging help out of laziness. I have spent
no less than four or five hours every day for more than a year
trying to learn enough about FETs, ferrite, class D/E, etc. so that
I might be in a better position to solve my own problems. Mostly I'm
just getting more and more confused, though the odd bit does sink
in. I do have a learning disability and my quest for understanding
on your level is even more elusive than my quest for a working
amplifier. I'm trying, honestly.

As for this particular amplifier, if that's the bottom line...
unwanted strays or leakage in the transformer is the problem... then
I can call this an inept failure on my part and put it to rest. I
don't think I'm going to win this one and I surely am not up to the
design challenge you suggest.

Honestly, and somewhat ashamed to admit it, I'm very tired of
constant study and building at this point. I just want a working
station. But the only path to that is continued work, study and most
likely a few more heartbreaking failures like this along the way so
onward I go.

I'm probably wrong but *if* I even begin to grasp your idea, it
sounds like 7 strands of #12 or #14 wire twisted evenly together and
then the big bundle wound on this core? If so... is that even practical?

Paul


On 04/10/2018 07:49 PM, jrusgrove@comcast.net wrote:
> Andy
>  
> Good idea on the multifilar winding.
>  
>>Everyone, stop, think. Stop clutching at straws
>  
> A fair number of these amplifiers have been built ... none of which
> exhibit the severe ringing that this particular one
> does. We're currently 'clutching at straws' to figure out what's
> different about this one.    
>  
> Jay W1VD
> 
>     ----- Original Message -----
>     *From:* Andy Talbot <mailto:andy.g4jnt@gmail.com>
>     *To:* LineOne <mailto:rsgb_lf_group@blacksheep.org>
>     *Sent:* Tuesday, April 10, 2018 5:01 PM
>     *Subject:* Re: LF: W1VD amp help - IR2110 and timing
> 
>     Everyone, stop, think. Stop clutching at straws
> 
>     Ringing like that, showing several cycles of oscillation has to
>     be  caused by a resonance at a higher frequency than the wanted one.
>     Resonances are caused by stray L and C.
>     Where is stray L coming from?
>     Leakage inductance.
> 
>     It's classic - seen on any SMPSU.   You have to get your
>     windings really well coupled.  A couuple of turns on a large
>     torroid I'm sure can't be completely leakage-free.  Unless Ur
>     were infinite.  So why not try multifilar windings ?
> 
>     If you want 1+1:2 turns ratio, for example,  twist four
>     conductors together and wind the resulting set the requisite
>     number of turns.   Use two of the strands in series for the "2"
>     secondary, and the other two as your 1+1 primary 
>     Multifilar gives you much tighter coupling
> 
>     Andy G4JNT
> 
> 
>     On 10 April 2018 at 21:45, Chris Wilson <dead.fets@gmail.com
>     <mailto:dead.fets@gmail.com>> wrote:
> 
> 
> 
>         Hello Paul, here's a link to my prototype build, the more I
>         think back
>         to bad drain waveforms the more convinced I am that the
>         major fix was
>         added  decoupling. I read Jay's very salient post about none
>         inductive
>         probing,  but  for  clarity  my scope captures are with two
>         X10 probes
>         with  the  hooked  spring  tips  on,  and the normal ground
>         leads both
>         clipped  to the driver board PCB ground plane, next to one
>         another, so
>         nothing careful done there to get those captures.
> 
>         As  we  seem  to  be  running  short  of  ideas re the amp
>         itself, bar
>         decoupling  and  short  gate  wires,  what about the LPF?? I
>         used blue
>         polypropylene  (I think...) caps of about 1500V DC> Each
>         section is in
>         its  own  totally sealed box, the mid toroid has two windows
>         milled in
>         the box with gauze over them for a PC processor fan to blow
>         air across
>         the  inductor. Each outer box feeds through to the mid one
>         via drilled
>         holes  of  about  10mm  diameter  with  the  inductor  wires
>         in Teflon
>         sleeving. Directly soldered. Caps are in each end box.
> 
>         Decoupling caps are at
>         http://www.chriswilson.tv/decoupling.jpg
>         <http://www.chriswilson.tv/decoupling.jpg>
> 
>         they  are done on the actual board of the MKII amp ;) But
>         functionally
>         there was no difference.
> 
>         Tuesday, April 10, 2018, 9:04:45 PM, you wrote:
> 
>         > OK, let's switch topics a bit.
> 
>         > I have a serious drain circuit ringing problem that most
>         builders
>         > apparently don't have. Many things change all but the
>         first peak of
>         > the ringing, but that first one is stubborn. It almost
>         seems like
>         > that first big peak is being "forced" to occur somehow.
> 
>         > I believe someone mentioned, though I cannot find it now,
>         that cross
>         > conduction (one phase starting to switch on before the
>         other is
>         > completely off) would exaggerate ringing.
> 
>         > I've become curious as to whether the timing in my amp is
>         correct.
>         > No one has really commented on this aspect. My driver board is
>         > unique and it would not be at all surprising it it has stray
>         > capacitance in excess of most!
> 
>         > Here are the two gate waveforms overlaid so you can see
>         the crossing:
> 
>         > http://www.n1bug.com/gates4-wdv13.jpg
>         <http://www.n1bug.com/gates4-wdv13.jpg>
> 
>         > And here are the drains similarly overlaid to show the
>         crossing:
> 
>         > http://www.n1bug.com/drains2-wdv13.jpg
>         <http://www.n1bug.com/drains2-wdv13.jpg>
> 
>         > *Is* this OK or could the timing be just a bit off? I lack the
>         > knowledge to interpret what I am looking at.
> 
>         > *If* it could possibly stand some improvement, do I have
>         control
>         > over it? I think the 1000pf caps and 15k resistors on the
>         IR2110
>         > inputs would affect this timing but I haven't been able to
>         work out
>         > exactly how or what to change if I wanted to experiment:
> 
>         > http://w1vd.com/137-500-KWRev3.0.pdf
>         <http://w1vd.com/137-500-KWRev3.0.pdf>
> 
>         > Paul
> 
> 
> 
> 
>         --
>         Best regards,
>          Chris                            mailto:dead.fets@gmail.com
>         <mailto:dead.fets@gmail.com>